Hot-air furnace



3 Sheets-Sheet 1.

(No Model.)

A; WILLIAMS. HOT AIR FURNACE.

%VE TQR W TNESSES:

ZM 79%M70.

(No Model.)

- I s Sheets-Sheet 2. A. WILLIAMS; HOT AIR FURNACE.

Patented Apr. 2, 1889.

INVENTOR N. PLTERS Mom-Lithographer. Washington, nc.

3 Sheets-Sheet 3.

A. WILLIAMS. HOT AIR FURNACE;

(No Model.)

Patented Apr, 2 1889.

Midi

N. PETERS. F'hnloLilhognphen Washinglun. D. C.

WITNESSES UNITED STATES PATENT OFFICE,

ALFRED WILLIAMS, OF PHlLADELPHIA, PENNSYLVANIA.

Hot-Al R FU RNACE.

S PEGTFIGATIOTN forming part of Letters Patent No. 400,86, dated April 2, 188?);

Application filed April 12 1888- Serial NOi 270,475. (No model.)

To all whom it may concern.-

Be it known that I, ALFRED WILLIAMS, of Philadelphia, in the county of Philadelphia and State of Pennsylvania, have made a new and useful Improvement in Hot-Air Furnaces for Heating Dwelling=Houses and the Like, of which the following is a full, clear, and exact description, reference being had to the drawings which accompany and form a part of this specification, in which Figure 1 is a vertical section through the middle of a furnace embodying my invention, showing the smoke-flue carried off to the side and the door for supplying the furnace with coal in front, and in which the cold-air flue is shown underneath as brought in from outside. Fig. 2 is a vertical section of the same furnace, taken upon a line at right angles to that of Fig. 1, and in which no external coldair flue or duct is employed. Fig. 3 is a transverse section of Fig. 1 or Fig. 2 upon the dotted line 00 00. Fig. 3 is a similar view, only oneehalf being shown, in which the internal vertical passages are divided to form a series of vertical compartments or channels; and Fig. 4 is a transverse section through the dotted line y y, Figs. 1 and 2.

The lettering in all the figures is uniform.

My invention relates to the construction of hot-air furnaces, such as are used for supplyingheated air to dwelling-houses, churches, halls, stores, factories, &c., in which greater simplicity and cheapness of construction and increased efficiency are secured, and in which the loss of heat from radiation from the furnace into thesurroundin g space is greatly diminished, and also in which the soot, dust, dirt, &c., which are liable to clog the passages of ordinary furnaces, are made to drop automatically into the fire-pot instead of by their deposit upon heated surfaces interfering with the heating of air in contact therewith and preventing free exit of the products of combustion, and in other improvements, which will be more particularly described herein after.

Referring now to the drawings, 0 is-the firepot of a furnace lined with fire-brick and having the upper portion of the fire-pot made integral with the lower part, as shown, or separate, as in some furnaces in general use.

.The grate B is of the ordinary form, as is the ash-pit E and drawer F, with regulatingapertures, as shown in Fig. 2.

From the periphery of the upper rim of the fire-pot O rises a Vertical wall, G forming a circular chamber, and which extends several feet above the fire-pot, as shown. This wall G I prefer to make of sheet metal, attached to the rim of the fire-pot O by rivets (shown at a) or otherwise.

A cover, G extends inward at the top of the sheet-metal wall G and from the inner margin of this cover G extends downward a wall, G, parallel with G and forming with it an annular chamber, G closed aboveby the cover G and communicating below with the fire-space A of the fire-pot O. The cover G is attached to the vertical walls G G above .by the rivets g g or a flanged seam; or the whole annular chamber may be cast in a single construction, if desired.

Attached to the lower margin of theinner vertical wall, G, is the crown-sheet of the furnace G, which is secured to G by rivets g, as shown, or otherwise. This crown-sheet G extends entirely over the fire-space A of the fire-pot C, so that the products of combustion and the radiated heat of the fire A impinge directly against its under side, and are thence deflected around the margins of the said crown-sheet G, and ascendthrough the annular space G between thevertical walls G and G escaping, as will be hereinafter described, at the upper part thereof.

The crown-sheet G, which is solid and.imperforate across its entire exposed surface, I prefer'to make convex upward in its middle and annularly convex downward at its margin, as shown, to increase the heating space and surface and retain the heated products of combustion, as well as facilitate the passage of the currents of air, as will be hereinafter described.

A door, D, and chute or passage 0 are provided in the side of the fire-pot C above the coal-space A to allow new supplies of fuel to be fed to the fire, and this passage 0 is inclined downward, as shown, so that the coal when shoveled into the furnace will not strike the lower outer surface of the annular chamber G but will clear its lower margin, as shown in Fig. 2.

The annular chamber G is provided at its upper part with a smoke-flue, M. (Shown in dotted outline in Fig. 2 and in section in Fig. 1.) Through this smoke-flue the products of combustion escape and are conveyed to the chimney or smoke-stack of the building in which the heating-furnace is located. This smoke-flue M may be provided with a damper, if desired.

It is obvious that the products of combustion rising through the annular chamber G having an exit only on one side and at its upper part, would be warped around, so that the opposite side of said annular chamber would be'comparatively cool, and t e products of combustion would rapidly escape in a twisted current converging to and passing through the said smoke-flue M, and that escaping in a highly-heated condition much of the available heat of the furnace would be wasted. To avoid this,beneatl1 the level of the said smoke'flue M, I provide an annular shelf, G which is attached by rivets g, or otherwise, to the inner vertical wall, G, of the annular chamber G and projects nearly across the said annular chamber, leaving a narrow crevice, g, between the free margin of said shelf G" and said outer wall, G, of said annular chamber IVhile the area of this space g is quite small for any limited segment of said vertical chamber, the aggregate for the whole circumference is equal to or greater than the area of the smoke-flue opening. I11 consequence the products of combustion deflected around the edges of the crown-sheet G and ascendin g through the vertical annular chamber G willbe arrested in their upward current by the shelf G and retarded and distributed so as to flow equally through the crevice g into the space G6 above the same. This space G forms an annular passage around the top of the annular chamber G and the products of combustion, having passed into this passage through the crevice g, are rapidly carried around to the smoke iiue and escape with a vigorous draft unimpeded by conflicting or intermingling currents. To prevent the loc gment of dirt, soot, ashes, &c., upon the upper surface of this shelf, and also to more effectually produce an eddy in and retard the upward flow of the products of combustion, I give this shelf a sharp downward slope from within outwardly, as shown in Figs. 1 and 2, and by this construction the flow is not only made more equal and slower, but the device is self-cleaning, so that any ashes or dirt will of itself roll down over the sloping surface and through the crevice and fall back into the fire-space A of the firepot C. In case any soot should adhere a tap inside from the door D against the inner walls of the annular chamber G will jar it loose and cause it to drop. The walls of the annular chamber, inclu ding the shelf G", I prefer to make of sheet iron or steel; but the crown-sheet should be made of cast metal or of heavy wrought or forged metal struck into shape while heated, as it is intended to resist heavy firing and to supply the greatest increment of heat to the currents of air forced over its upper surface, as will be now described. All the joints should be made air-tight, either by riveting or by forcing the sheet-metal tubes over their seats upon the cast or wrought metal parts, as is done with boiler-tubes, orsometimes in drums for heating-furnaces. What is required is a tight joint which will not open under the expansion produced by the heat of the furnace or the cooling of the same, and such joint may be produced by any of the processes of manufacture in ordinary use.

It will be seen that we now have a furnace provided with a fire-pot, &c., and a chamber above the same and a crownsheet, in which the crown-sheet is brought down directly over the fire-space A and relatively very near to it, so that the products of combustion act against it at their highest temperature, and in which the direct heat of radiation from the incandescent coal is also thrown directly upon it instead of into the rising products of combustion, as in ordinary furnaces having large cyli n d rical. chambers above the fire-pot, and that in this furnace the upward currents of the products of combustion ascend through an annular chamber, heating the opposite walls thereof with a heat decreasing as the currents ascend and as their heatis dissipated into the space" around the said annular chamber. What is now required is to bring currents of air to be heated into contact with these surfaces in such manner that the cooler currents shall receive heat from the cooler parts of this furnace, and that as the currents of air advance they will constantlypass over hotter and hotter parts of the heatingfurnace, and finally be distributed for use. If these currents of air follow this course without admixture with fresh supplies, and if they pass steadily alongin a constantlyflowing stream, growing hotter and hotter as they advance, the said currents of heated air will move forward with a high velocity, and the amount of hcatrcceived from the furnace will be greater in the same proportion, or, conversely, the fuel required to heat this air will be less. Interfering currents of air, composed of hot currents commingled with cooler ones, retard the flow, and by an amount of heat de rived from an average between such currents permit the heat of the furnace to escape at a relatively high ten'iperature.

In my furnace, as shown, the least heat of the furnace just before its exit comes in contact with the coolest currents of air, and the hottest currents of air just before their exit into the building come in contact with the hottest part of the furnace, and so for each intermediate flow of the currents of air growing hotter and products of combustion growing cooler, and also that each part of the furnace proper is jacketed or surrounded wit-h a current of air ready to take up all the heat which such part of the furnace is capable of imparting, and that this current of air,

IIO

and the casing having received its heat, passes onward to a hotter part to receive more, and so on until its final exit into the building, so that scarcely any of the heat of the furnace is wasted in heating the cellar or basement, but the whole supply, practically, is delivered through the hot-air pipes into the rooms above.

The currents of air to be heated are formed and directed by the following means: Over and above the annular combustion-chamber G forming the upward annular extension of the fire=pot O, is placed an annular air-casing, which forms an external vertical passage for the ascending cold air, a transverse passage inward over the top of the annular combustion-chamber, and an internal vertical passage for the descending partly-heated air in contact with the inner surface of the annular combustion-chamber G said internal vertical passage open at its lower margin, so as to leave a free space between said free lower margin and the upper surface of the crownsheet of the furnace proper, the centralspace within the walls of said descending vertical passage forming a vertical tube, through which the thoroughly-heated air, after turning around the lower free margin of the descending vertical passage, ascends.

H, Fig. 1, shows the external casing of my heater, which may be of brick, if desired, but which I show as of metal in what is called a portable heater. This external casing surrounds the furnace proper, and the door D and passage 0 extend through the same transversely from the outer air to the fire-pot space A, Fig. 2.

At K, Fig. 1, is shown a water-evaporating tank, which is riveted to this casing at k k, passes through the same, and faces flush against theannular combustion-chamber. A cover closes the projecting portion, which being removed water is admitted to the space L. The heat of the annular combustion-chamber evaporates a portion of this water, which vapor ascends through the opening is and moistens the air. The inner end of K, I prefer to make with a wall of its own, facing against the annular combustion-chamber, as expansion and contraction are allowed for, and the heat of evaporation is not so great as if the'water rested against the combustionchamber itself. The smoke-flue M also passes through the external casing, H, as shown in Fig. 1. The walls of H are made air-tight, except at the bottom, where air-supply openings H H are shown, deriving their supply of air in Fig. 1 from an external feeder, H, and in Fig. 2 from the basement or other place in which the heater may be located. These inlets may be controlled by checkvalves, if desired. The ash-pan of the furnace proper, E, projects through the space H H, just over these inlets H H which may be few or many in number, as desired. The vertical casing or wall H, inclosing the furnace proper, leaves an airspace, H, between the external walls of the furnace proper and the internal wall of the casing H. At its lower part this air-space H is enlarged by reason of the contract-ion of the fire-pot O beneath; but in its upper portion it is parallel with the external wall of the annular combustion-chamber G so that a volume of air passing up through the inlets H H will first travel slowly, absorbing the heat of the fire-pot O, and then, as the passage H is narrowed above, will ascend more rapidly, taking additional heat from the closer contact which it makes with the annular combustion-chamber G along the external wall of which, G ,it ascends. The external casing, H, after extending a suitable distance above' the annular combus= tion-chamber G to give free passage across the top of the same, extends horizontally inward over the top of said annular chamber G having laterally-closed sides, so as to form a continuous passage out of contact with the distribution-chamber H above, as shown at H, Figs. 1 and 2; or, if the casing H be of brick this horizontal extension is built into the brick wall, so as to extend across the top of the annular combustion chamber and within the inner margin of the same, as shown. This inwardlyproj ecting part H of the casing H extend inward beyond the inner lineof the chamber G and is then continued downward by an inner casing, H forming an air-tight closed joint at h, Figs. 1 and 2, ending below, so as to leave a free space, IF, between the free margin of H and the top surface of G,

and producing a passage between the casing H and the inner wall, G, of theannula'r combustion-chamber. The space H forms a communication between the downward hotair passage H and the central upward hotair passage, H at the lower margins thereof. This inner casing, 1 forming a circle in section,(see Fig. 3,) when in place is a cylinder open below, so that a free passage is had within said cylinder for-the ascending current of heated air. 'The walls H H H surround the furnace proper and the annular combustion-chamber G and form an annular casing, which serves to hold the currents of air in contact and thoroughly heat them against the heated parts of the furnace proper, and also prevents admixture of more heated with less heated portions of the atmospheric current, and guides them forward toward the central and hottest part of the furnace. While I show this casing provided with angles at the lines of junction of the vertical with the horizontal parts, if preferred, 1 make them with rounded corners or give them any curvature desired.

Resting upon the outer casing, H, I show the conical cover-N, which extends over the whole heater. If built of brick, this cover may also be of brick and may be fiat or arched.

Into the under side of this conical cover N opens the central passage, H and from the Ioo upper side lead the heat-pipes J J which distribute the heat to various parts of the struct ure to be heated. When made of metal, as shown, I slip this conical cover, which is made in a single piece, riveted to form a cone, upon the outer casing, H, as is usual in drums of heaters, 850. These flangesv are shown at h 71, Figs. 1 and 2. I also provide, if necessary, a marginal flange or lip, 71., around the circumference of the conical top or cover, and I fit over the whole cone at protecting cover or jacket of non-combustible felt or plastic composition, such as is used for covering steam-boilers, &c., and preventing escape of heat. This non-conducting covering P rests against the lip. 12., and is pierced for the pipes J and J, and may be extended along the same, if preferred.

An examination of Figs. 1 and 2 will now show the operation of my heater. The furnace being properly heated, the radiated heat will play against the crown-sheet G, and it will become intensely heated, the products of combustion assisting and then being turned around the free margin of the crown-sheet and ascending through the vertical annular combustion-chamber G the ascending current will be checked by the shelf G passing through the crevice g, and equalized all around the annular crevice by its narrowness. The products of combustion enter the annular passage G and are rapidly drawn around the same to the smoke-flue M, through which they escape to the chimney, the soot and ashes falling back from the sloping shelf G into the fire-space A. At the same time the air entering the annular casing through the inlets H H comes in contact with the external body of the fire-pot C, and as the space is considerable the cold air becomes gradually warmed, ascending slowly. As it reaches the narrower part of the passage H alongside the highly-heated wall G it ascends rapidly, drawing heat from the wall G as it ascends. Reaching the top of the annular combustionchamber G the current of air turns inward, still in contact with the top plate, G, of the annular combustion-chamber, G below and only separatedby the plate H from the heated space 11 above, the currents being henceforth surrounded with opposite currents of highly-heated gases. Turning downward within the annular combustion-chamber G and between its highly heated inner wall, G, and the inner casing, H, which only separates it from the still hotter air-space 11*, the descending current H is thrown directly downward upon the upper surface of the crown-sheet G, which is the hottest part. of the furnace. Owing to the curvature of this crown-sheet G, the current follows it, as shown by the arrow, until it turns around the lower free margin of H and ascends through the inner casing, H to be distributed above. The currents thus not only grow hotter as they approach the central axis of the furnace, but are concentrated by constantly occupying more and more contracted cylinders, until finally the whole volume is thrown upward through the central cylinder in its condition of highest temperature. WVhile at first glance the downward current H might seem ,to retard the general delivery, yet this is only apparent, as the heights of the inlets of the cold air and of the exit of hot air control the air-pressure and forward movement of the inclosed currents, the gradually-increased heat of the current as it advances assisting greatly in giving force and vigor, as well as volume, to the out put of heated air. In other words, the pull of the ascending very hot current H re-enforced by the push of the ascending warm currentH, supplemented by the weight of the cold atmosphere without, much more than merely neutralize the downward flow of the current in the passage I1", and the hot air is poured forth above with a volume and high temperature not otherwise easily secured. It will be observed that the currents are all direct and unmixed, and that no averages made by cold air mingled with hot are produced, but that each unit of heat is taken up and constantly planted one step forward as the current advances, holding its own and receiving new units of heat for every stage of progress, and that every degree of heat communicated from the hottest air, H", to the less heated downward current Hi through the inner casing, H, is immediately carried around the free lower edge of H and itself becomes the ascending current, receiving new heat from the crown-sheet G as it advances, and so on for the other passages of the currents through the heater, and also that the products of combustion rising through the vertical annular combustion-chamber G are cooled outside by the ascending current of nearlycold air H and the descending current 11.", cooler at its upper part, and the temperature of the narrowannular chamber G surrounded with currents of cooler air, rapidly sweeping over its surfaces, cools toward its upper part, and the products of combustion pass off at a IIO comparatively low temperature, the hottest part of the furnace being reserved to act upon the current of air gradually growing hotter just before its final delivery and utilization, and that the same heat which acted upon the crown-sheet G in its highest temperature afterward passes up the annular chamber G to act upon the cooler currents of air as they advance from the outer to the inner and hotter parts ofthe heat-er.

. Various modifications will suggest themselves to an intelligent mechanic without departing from the principles of my invention, as herein shown.

In Fig. 3'" I show the vertical annular combustion-ehamber G divided by a series of vertical partitions, G to assist in preventing deflection of the ascending currents of the products of combustion, and I also show vertical partitions between the inner wall of the annular combustion-chamber G and the inner casing, H, so as to divide the passage H into a series of vertical channels; but I prefer to use the simpler construction shown in the other figures.

Sometimes I apply my invention to a stove which is used for heating a room in a dwelling, for instance, and the surplus heat is used to heat rooms above. In this case I dispense with my outer casing, H, leaving the fire-pot and the outer wall of the annular chamber G to heat the room which the stove occupies, and

use only an inner casing, H, as shown, with its passage H downward between H and G. I carry this casing I-I upward above the level of the top of the furnace to supply a central column of heated air through the central passage, H and draw my air to be heated from the atmosphere of the room over the top of the annular chamber G the currents passing downward through the passage H radially inward through the space H over the crownsheet G, and vertically upward through the central passage, H In such case, if desired, I rest the casing, by studs, uponthe crownsheet G or suspend it by brackets from the top of G or I distribute this extra heat, if desired, through the central passage, H extended above the level of the top of the annular chamber G, into the room occupied by the stove itself, greatly adding to the. heat produced thereby.

Having now described my invention, what I claim, and desire to secure by Letters Patent, is-

1. In a heating-furnace provided with firepot and contained fire-space and an annular combustion chamber communicating with said fire-space and rising above the crownsheet G, the smoke-flue M, leading from the upper part of said annular combustion-chamber at one side thereof, and the shelf G surrounding and contained within the said annular chamber beneath the exit of said smokefiue, there being a crevice, 9 extending around the said annular chamber between the free edge of said shelf and the opposite wall and adapted to cause the products of combustion to ascend vertically into the space above said shelf and be thence drawn laterally into said smoke-flue M, substantially as described.

2. In combination with the fire-pot O, firespace A, crown-sheet G, and annular combustion-chamber G the smoke-flue M, opening from the upper partof said chamber G at one side thereof, and the downwardly-sloping shelf G attached at its upper margin to one of the walls of said annular combustion-chamber beneath said smoke flue and extending around within the same, there being the crevice g around the free margin of said downwardly-sloped shelf, the whole constructed substantially as and for the purposes described.

3. An air-heating furnace consisting of firepot O and its attachments, fire-space A, transverse imperforate crown-sheet G, and annu lar combustion-chamber G surrounding and extending above the level of said crownsheet, with smoke-flue M leading from one side of said annular combustion-chamber at the upper part thereof, in combination with an annular air-casing surrounding said furnace, having air-inlets beneath said casing closed above, and extendedinwardly over said annular combustion-chamber G and downwardly within the inner walls thereof, forming the annular inward passage H between the lower free margin of H and the upper surface of the crown-sheet G, and the central upward air-passage,'H said casing adapted to convey a current of air to be heated upward and inward over the top of said combustionchamber G thence downward within the same, and thence inward beneath the free margin of wall H and finally upward in a central column of highly-heated air, the products of combustion being carried off from the upper part of said combustion-chamber G -at one side thereof, substantially as described.

- 4. In combination with the furnace A O,

imperforate crown-sheet G, attached to the in- 0 ner wall, G, of annular combustion-chamber G said combustion chamber surrounding and rising above the level of said crown-sheet, open beneath into fire-space A, closed above by the wall G and having external wall, G 5

attached to fire-pot O, the smoke-flue M,

leading from the upper part of said annular combustion-chamber G at one side thereof,

and an air-guiding casing consisting of external vertical wall, H, surrounding said fur- 10o nace and provided with air-inlets H H beneath, closed transverse top H attached to the upper part of wall H and extended inwardly over andwithin the annular combuse t-ion-chamber G inner vertical wall, H attached-to and depending from the inner margin of H and terminating beneath in a free margin, leaving annular space H continuously extending around and over said crownsheet G, and central vertical air-passage, H

the whole constructed to operate substantially as and for the purposes herein shown and described.

5. In combination with the air-distributing chamber H above-the level of aheating-fun 1 I 5 nace, and provided with one or more hot-air exits, J J, the upward central air-passage, H opening centrally into H annular downward air-passage H leading at its lower part,

II", into H transverse passage inward over beneath to passage into H above, said pas- V sages separated from each other by continuous annular walls and leading into each other through continuous annular passages from said inlets H to said distribution-chamber H substantially as and for the purposes described.

6. In a furnace for heating buildings by hot air conveyed through passages thereof, the

furnace proper having ash-pit, fire-pot,en-

trance for fuel, and the fire-space A, and over said fire-space, relatively near the same, the transverse crown-sheet G, formed entire and imperforate, and the annular combustionchamber G, connecting the outer margin of said crown-sheet with the wall of said firepot, and rising above the level of and surrounding said crown-sheet, and having smokeflue M, leading from the upper part of said annular combustion-chamber G, in combination with said furnace, an annular air-casing consisting of outer wall, ll, external to said furnace, extending above the level of said annular casing and pierced by said smokeflue M, having external air-inlet, 1'1 beneath, and transverse top H, continuing said casin II over and within the vertical inner line of said annular combustion-chamber, and downward inner wall, H, continuing said casing H H downward within said annular combustionehamber G, havingannular space H between said wall II and said combustion-chamber G, and central passage, ll, over the center of said crown-sheet G, separated from said fire-space A thereby, and the inward passage H connecting the lower part of annular air-space II with lower part of central passage, H said passage ll forming a central air-passage upward, together with one or more air-dis tributing pipes, J, above the level of the said furnace, substantially as described.

7 i In combination with a stove or furnace having transverse crown-sheet over and rela tively near the fire-space A, said crown-sheet formed entire without opening or perforation therein, and an annular combustion-chamber surrounding said crown-sheet above the level of the same and attached by its inner wall to the periphery thereof and by its outer wall to the upper part of the fire-pot 0, closed above at G and having sn1oke-flue M leading from said annular combustion'chamber G, the annular wall II extendin downward within the inner walls of said annular combustionehamber, having vertical downward passage H between said wall H": and said chamber G, and an air-inlet external to its upper part over said combustion-chamber, said wall II extending downward near to and above said crown-sheet G and leaving annular passage H together with the central upward air-passage, H, receiving a current of air through the said passage H from said downward passage H", the whole constructed to operate substantially as described,

8. The combination of stove or furnace A C D E, solid imperforate erown-sheet G, annular combustion-cha1nber G, surrounding said crown-sheet and extending above the level of the same, smoke-flue M, leading from said annular combustion-chamber, with the annular wall ll, extending downward within the inner wall, G, of said COIllbllSt-lOll-Chtlllher and forming an annular downward passage, II, open above externally and terminating beneath in a freemargin, leaving annular space H between the upper surface of said erownsheet G and said free margin, said space II continuous around and within the periphery of said crown-sheet, and internal ascending passage, ll, connected therewith and extending above the upper surface of said furnace, substantially as described.

9. In combination with a heatingfurnace having asl1pit, fire-pot, and a lire-space, A, and above and relatively near said fire-space, a transverse crown-sheet, G, attached by its periphery to the inner wall, G, of the annular co1nbustion-chamber G, the outer wall, G supported by said lire-pot, said combustionchamber closed above by transverse wall G, and having smoke-flue M leading therefrom, and beneath said smoke-flue the annular shelf G", extended around within said chamber G, there being a crevice, g, the air-casing surrounding said furnace and consisting of external annular wall, ll, having inlets H inturned top ll, forming transverse passage over and within the inner wall, G, of annular combustion-chamber G, downwaivlly-turned inner wall, ll, forming downward passage ll", there being an inward passage,l 1 between the lower margin of H and the upper surface of G, and ascending cylindrical passage ll. within. the wall II and connected with passage ll through space ll, chamber H above and connected with ll, cover N, and one or more hot-air-distrilniting pipes, J J, substanti ally as and for the purposes herein set forth.

10. In a port-able metallic hot-air furnace for heating buildings, thef urnace proper, havin g fire-space A, crown-sheet G, relatively near said fire-space and attached to inner wall of combustion chamber, annular combustionchamber G, and air-casing consisting of outer wall, ll, inturned top ll, connected therewith, and inner wall, ll, depending therefrom, having ascending eold-ai r passage II surrounding the outer wall of said furnace, having inlets H beneath, transverse air-passage inward over the top of annular combustion-chamber G, downward air-passage ll", inward passage lllaseendin g central passage, ll", chamber I 1. above the same, distributing-pipes J J, and metallic cover N, together with the supplemental non-condueting cover P, adapted to prevent escape of heat from said chamber ll before distribution thereof, substantially as described.

11. In a hot-air furnace, in combination with a fire-space, A, and annular combustionchamber G, and an imperforate crown-sheet, G, within said annular chamber G, closing the space within the inner walls, G, thereof and relatively near the fire-space A, the double annular casing II II II, there being transverse passages beneath II and ll, forming continuous annular passages ll upward, transverse passage beneath I'l inward, ll" downward, ll inward, and central cylindrical upward passage, ll, said passages continuous and adapted to convey currents of air in contact with more and more highly-heated parts of said furnace from firepot C to center of crown-sheet G as said currents of air advance along the surfaces of said furnace, together with smoke-flue M, leading from the upper part of said annular combustion-chamber G and receiving the products of combustion at the lowest temperature from contact with the coolest currents of air in their ascentthrough passage H substantially as described.

12. In a hot-air furnace, an annular combustion-chamber, G supported by its outer wall, G upon the margins of fire-pot O, having annular top G attached hermetically to outer wall, G and to inner wall, G, imperforate crown-sheet G, attached hermetically to lower margin of said inner wall, G, and supported thereby, in combination with a double annular air-casing consisting of vertical outer wall, H, provided with air-inlets I-l beneath, having annular top H hermetically attached to and supported by said wall H and hermetically attached to and supporting inner annular wall, H said wall H terminating in a free margin near to and above said crown-sheet G, leaving space H and internal upward passage, H*, the said furnace and said air-casing independent of each other and each self-supporting, substantially as described.

13. In a stove or furnace, the fire-pot C, annular combustion-chamber G solid imperforated crown-sheet G, attached to inner wall of the combustion-chamber, internal annular casing, H downward annular passage H beannular passage, H connected externally with the lower part of downward air-passage H and internally with the lower part of upward central air-passage, H together with smoke-flue M, leading from said annular combustionchamber G substantially as and for the'purposes set forth.

14." In combination with the fire-pot C, firespace A, annular combustion chamber G smoke-flue M, leading therefrom, outer aircasing, H, inwardly-extended transverse top H having joint h, and downwardly-extended inner wall, H, having joint h there being a space, H beneath wall H connecting the downward passage H and upward central passage, H the solid imperforate crown-sheet G, extended over and relatively near the firespace A, hermetically attached to thelower margin of inner wall, G, of annular combustion-chamber G said crown-sheet having an upward convexity in the center thereof beneath said central'passage, H and an annular concavity in its upper surface beneath the free margin of said annular wall H substantially as described.

ALFRED WILLIAMS.

Witnesses 1' F. T. CLARK, V CHAS. E. FELL, Jr. 

